Method for secure time-stamping of digital documents
First Claim
1. A method of time-stamping a digital document which comprises:
- a) transmitting a digital representation of said document from an originator to an outside agency;
b) creating at said outside agency a receipt comprising a digital representation of then current time and at least a portion of a digital representation of said digital document; and
c) certifying said receipt at said outside agency by means of a verifiable digital cryptographic signature.
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Accused Products
Abstract
A system for time-stamping a digital document, including for example text, video, audio, or pictorial data, protects the secrecy of the document text and provides a tamper-proof time seal establishing an author'"'"'s claim to the temporal existence of the document. Initially, the author reduces the document to a number by means of a one-way hash function, thereby fitting a unique representation of the document text. In one embodiment of the invention the number is then transmitted to an outside agency where the current time is added to form a receipt which is certified by the agency using a public key signature procedure before being returned to the author as evidence of the document'"'"'s existence. In later proof of such existence, the certificate is authenticated by means of the agency'"'"'s public key to reveal the receipt which comprises the hash of the alleged document along with the time seal that only the agency could have signed into the certificate. The alleged document is then hashed with the same one-way function and the original and newly-generated hash numbers are compared. A match establishes the identify of the alleged document as the time-stamped original. In order to prevent collusion in the assignment of a time stamp by the agency and thus fortify the credibility of the system, the receipt is linked to other contemporary receipts before certification by the agency, thereby fixing a document'"'"'s position in the continuum of time. In another embodiment, a plurality of agencies are designated by means of random selection based upon a unique seed that is a function of the hash number of the document to be time-stamped. Thus being denied the ability to choose at will the identity of an agent, the author cannot feasibly arrange for falsification of a time stamp.
258 Citations
20 Claims
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1. A method of time-stamping a digital document which comprises:
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a) transmitting a digital representation of said document from an originator to an outside agency; b) creating at said outside agency a receipt comprising a digital representation of then current time and at least a portion of a digital representation of said digital document; and c) certifying said receipt at said outside agency by means of a verifiable digital cryptographic signature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for the secure time-stamping of a digital document
characterized in that a) a digital representation of said document is transmitted from an originator to an outside agency; -
b) said outside agency creates a receipt comprising a digital representation of then current time and at least a portion of a digital representation of said digital document; and c) said receipt is certified al said outside agency by means of a verifiable digital cryptographic signature scheme. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for time stamping a particular digital document comprising
(a) forming a collection of hash values by hashing each group comprised of one or more digital documents in an accumulation of digital documents, including said particular digital document, generated over a period of time, (b) forming a single hash value representative of said collection of hash values, and (c) creating a time stamp receipt for said particular digital document by associating an indication of then current time with said single hash value. .Iaddend. .Iadd.20. A method for time stamping a particular digital document comprising (a) forming a collection of digital values by applying a deterministic function to each digital document or group of digital documents in an accumulation of digital documents, including said particular document, generated over a period of time, (b) forming a single digital value from said digital values in said collection, and (c) creating a time stamp receipt for said particular digital document by associating an indication of then current time with said single digital value. .Iaddend. .Iadd.21. A method for time stamping a particular digital document in a series of digital documents comprising the steps of (a) forming a receipt comprising at least a portion of a digital representation of said particular digital document and a digital representation of time then current as of the forming of said receipt, (b) forming at least one different receipt comprising at least a portion of a digital representation of at least one different digital document in said series of digital documents and a digital representation of time then current as of the forming of said at least one different receipt, and (c) utilizing said receipts to form a composite receipt which is thereby
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20. fixed in the continuum of time. .Iaddend. .Iadd.22. A method for time stamping a particular digital document in a relatively continuous flow of digital documents comprising the steps of
(a) forming a receipt comprising at least a portion of a digital representation of said particular digital document, (b) forming at least one different receipt comprising at least a portion of a digital representation of at least one different digital document in said relatively continuous flow of digital documents, and (c) utilizing said receipts to form a composite receipt which is thereby fixed in the continuum of time. .Iaddend. .Iadd.23. A method for time stamping a particular digital document comprising the steps of (a) at an originator, forming a particular digital value representative of said particular digital document by applying a deterministic function to said particular digital document, (b) transmitting said particular digital value to a time stamping agency, (c) at said time stamping agency, forming a collection of digital values, including said particular digital value, and forming a single digital value from the digital values in said collection, and (d) creating a time stamp receipt for said particular digital document by associating with said single digital value a representation of then current time. .Iaddend. .Iadd.24. The method of claim 23 wherein said particular digital value representative of said particular digital document is a particular hash value, said deterministic function is a hash function, said collection of digital values including said particular digital value is a collection of hash values including said particular hash value, and said single digital value is a single hash value representative of said collection of hash values. .Iaddend. .Iadd.25. A method for time stamping a particular digital document comprising the steps of (a) at an originator, forming a particular digital representation of said particular digital document, (b) transmitting said particular digital representation to a time stamping agency, (c) at said time stamping agency, forming a receipt comprising at least a portion of said particular digital representation of said particular digital document, (d) at said time stamping agency, forming at least one different receipt comprising at least a portion of a digital representation of at least one different digital document, and (e) forming from said receipts a composite receipt which is thereby fixed in time. .Iaddend.
Specification
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- Resources
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Current AssigneeTelcordia Technologies Incorporated (Telefonaktiebolaget LM Ericsson)
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Original AssigneeBell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
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InventorsStornetta, Wakefield S. Jr., Haber, Stuart A.
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Primary Examiner(s)Gregory, Bernarr E.
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Application NumberUS08/156,120Time in Patent Office554 DaysField of Search380/3-5, 380/9, 380/10, 380/28, 380/30, 380/49, 380/50US Class Current713/177CPC Class CodesH04L 2209/60 Digital content management,...H04L 9/3297 involving time stamps, e.g....
